Display screen or portion thereof with a graphical user interface



The FIGURE is a display screen or portion thereof with a graphical user interface showing our new design.

The features in broken lines form no part of the claimed design. The innermost broken line circle represents the display screen. The broken lines within the display screen represent portions of the graphical user interface. The rest of the broken lines represent an electronic device. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 